According to the conventional process of fabricating a semiconductor device, to perform a process of thinning a wafer (e.g., a back lap process), a carrier is attached to the wafer using an adhesive material. If a thickness of the adhesive or a distance between the wafer and the carrier is not uniform, the wafer may be polished to have a non-uniform thickness, during the back lap process. In this case, when through silicon vias are formed through the wafer, protruding lengths of the through silicon vias may vary from position to position, and thus, the through silicon vias may be broken.